The photographic emulsion layers and other hydrophilic colloid layers of silver halide photographic materials are often colored to allow light in a specific wavelength region to be absorbed.
When the spectral composition of light which enters a photographic emulsion layer must be controlled, a colored layer is usually provided on the side of the photographic emulsion layer which is farther away from the support. Such a colored layer is called a filter layer. When there are two or more photographic emulsion layers, a filter layer is often provided therebetween.
A colored layer called an antihalation layer is often coated between the emulsion and the support or on the back of the support to prevent the image from being fogged, that is, to prevent halation. Halation is an effect in which light which is diffusely transmitted by the emulsion and strikes the back surface of a transparent support is partially or totally reflected back to the emulsion and reexposes it at a considerable distance from the initial point of entry See T. H. James, The Theory of the photographic Process 579,599 (4th ed. 1977). When there are two or more photographic emulsion layers, an antihalation layer is often provided therebetween.
The photographic emulsion layer is sometimes colored to prevent the sharpness of an image from being lowered by the scattering of light in the photographic emulsion layer (this phenomenon is generally called irradiation).
These hydrophilic colloid layers to be colored usually contain dyes. The dyes must meet the following conditions:
(1) The dyes must have proper spectral absorption according to purpose. PA1 (2) The dyes must be photochemically inert, that is, they must not have any adverse effect on the performance of the silver halide emulsion layers in a chemical sense. For example, the dyes must not cause lowering of sensitivity, fading of the latent image, fogging, etc. PA1 (3) The dyes must be decolorized during the course of photographic processing or must be dissolved out into processing solutions or rinsing water so that no deleterious color is left behind in the photographic material after processing. PA1 (4) The dyes must not diffuse from the dyed layer into other layers. PA1 (5) The dyes must have excellent stability in solution or photographic materials with the passage of time and not discolor.
Particularly, when the colored layer is a filter layer or an antihalation layer provided on the same side of the support as the photographic emulsion layer, it is necessary that the colored layer be selectively colored and that other layers not be substantially affected by the coloration. Otherwise, the coloration may have a deleterious spectral effect on other layers, and the effect of the colored layer as a filter layer or an antihalation layer will be diminished. However, when a dye-containing layer and another hydrophilic layer are brought into contact with each other in a wetted state, there is frequently a problem in that a part of the dye diffuses from the former into the latter. Many attempts have been made in the art to prevent the diffusion of the dye from occurring.
For example, U.S. Pat. Nos. 2,548,564, 4,124,386 and 3,625,694 disclose a method wherein a hydrophilic polymer, as a mordant, having a charge opposite to a dissociated anionic dye is allowed to coexist with the dye, and the dye is localized to a specific layer by an interaction between the polymer and the dye molecule.
However, the dye fixing/decolorization method using the mordant requires the use of a large amount of the mordant in comparison with the amount of the anionic dye, and hence the thickness of the colored layer inevitably becomes thick. For example, when the colored layer is used as the filter layer of a photographic material for photographing, the increase of the thickness of the layer causes a problem in that the sharpness of the resulting image is deteriorated. Further, in the system using the mordant, the mordant must not interfere with the sensitizing dye used for silver halide emulsions. However, the decoloration performance is not on a satisfactory level with the development of high-quality images and rapid processing of photographic materials in recent years.
A method wherein a specific layer is dyed with water-insoluble solid dyes is disclosed in JP-A-56-12639 (the term "JP-A" as used herein means an "unexamined published Japanese patent application"), JP-A-55-155350, JP-A-55-155351, JP-A-63-27838, and JP-A-63-197943, European Patents 15,601, 274,723, 276,566 and 299,435, U.S. Pat. No. 4,803,150 and WO (PCT) 88/04794.
Further, a method wherein a specific layer is dyed with fine metal salt particles having a dye adsorbed thereon is disclosed in U.S. Pat. Nos. 2,719,088, 2,496,841 and 2,496,843 and JP-A-60-45237.
These dyeing methods are excellent in terms of fixability/decolorizability, but problems often occur, for example, when the dyes are to be used as filter dyes for light having a specific wavelength.
A method wherein oil-soluble dyes together with high-boiling organic solvents are dispersed is disclosed in JP-A-61-204630, JP-A-61-205934, JP-A-62-32460, JP-A-62-56958, JP-A-62-92949, JP-A-62-222248, JP-A-63-40143, JP-A-63-184749 and JP-A-63-316852.
However, the use of the high boiling organic solvents causes softening of the colored layer and lowering in the strength of the layer. Accordingly, a larger amount of gelatin is required and as a result, the thickness of the layer is increased contrary to demands for thinning the thickness of the layer.
JP-B-51-39853 (the term "JP-B" as used herein means an "examined Japanese patent publication") JP-A-51-59943, JP-A-53-137131, JP-A-54-32552, JP-A-54-107941, JP-A-56-126830, JP-A-58-149038, and U.S. Pat. Nos. 4,199,363, 4,203,716 and 4,990,435 disclose a method wherein a polymer is impregnated with a solution of a hydrophobic material such as a dye in an organic solvent to form a polymer latex loaded with the hydrophobic material. This method avoids the problem caused by the use of the high-boiling organic solvents since the polymer is used. However, there are disadvantages in that the stability of polymer latex particles is insufficient during impregnation, and the particles are liable to agglomerate; a large amount of the polymer must be used to sufficiently impregnate the hydrophobic material therewith; much time and labor are required for the removal of a water-soluble co-solvent used for the impregnation; and the process itself requires a long time and is complicated.
The present inventors have made studies and have found that when a dispersion obtained by emulsifying and dispersing a solution containing a water-insoluble, organic solvent-soluble polymer and an oil-soluble dye is used, a specific layer can be selectively dyed and the dye can be decolorized in processing stages without having any adverse effect on the absorption characteristics of the dye and the strength of the layer. However, the compatibility of the organic solvent-soluble polymer with the oil-soluble dye is not always sufficient and problems are encountered, such as that solubility of the dyes in organic solvents is low or that when high-melting dyes are used, the absorption zone is broadened and the absorption intensity at the maximum absorption wavelength is lowered.
These problems can be solved to some degree by increasing the proportion of the polymer to be dispersed or by using the high-boiling organic solvent together with the dye dispersion. However, any of these methods results in an increase of the thickness of the dyed layer contrary to demands of thinning the thickness of the layer to provide an image of high quality. Hence, the degree of the improvement is still not on a satisfactory level.